xref: /openbmc/linux/arch/mips/mm/fault.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
1 /*
2  * This file is subject to the terms and conditions of the GNU General Public
3  * License.  See the file "COPYING" in the main directory of this archive
4  * for more details.
5  *
6  * Copyright (C) 1995 - 2000 by Ralf Baechle
7  */
8 #include <linux/signal.h>
9 #include <linux/sched.h>
10 #include <linux/interrupt.h>
11 #include <linux/kernel.h>
12 #include <linux/errno.h>
13 #include <linux/string.h>
14 #include <linux/types.h>
15 #include <linux/ptrace.h>
16 #include <linux/mman.h>
17 #include <linux/mm.h>
18 #include <linux/smp.h>
19 #include <linux/vt_kern.h>		/* For unblank_screen() */
20 #include <linux/module.h>
21 
22 #include <asm/branch.h>
23 #include <asm/mmu_context.h>
24 #include <asm/system.h>
25 #include <asm/uaccess.h>
26 #include <asm/ptrace.h>
27 #include <asm/highmem.h>		/* For VMALLOC_END */
28 
29 /*
30  * This routine handles page faults.  It determines the address,
31  * and the problem, and then passes it off to one of the appropriate
32  * routines.
33  */
34 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write,
35 			      unsigned long address)
36 {
37 	struct vm_area_struct * vma = NULL;
38 	struct task_struct *tsk = current;
39 	struct mm_struct *mm = tsk->mm;
40 	const int field = sizeof(unsigned long) * 2;
41 	siginfo_t info;
42 
43 #if 0
44 	printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(),
45 	       current->comm, current->pid, field, address, write,
46 	       field, regs->cp0_epc);
47 #endif
48 
49 	info.si_code = SEGV_MAPERR;
50 
51 	/*
52 	 * We fault-in kernel-space virtual memory on-demand. The
53 	 * 'reference' page table is init_mm.pgd.
54 	 *
55 	 * NOTE! We MUST NOT take any locks for this case. We may
56 	 * be in an interrupt or a critical region, and should
57 	 * only copy the information from the master page table,
58 	 * nothing more.
59 	 */
60 	if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END))
61 		goto vmalloc_fault;
62 #ifdef MODULE_START
63 	if (unlikely(address >= MODULE_START && address < MODULE_END))
64 		goto vmalloc_fault;
65 #endif
66 
67 	/*
68 	 * If we're in an interrupt or have no user
69 	 * context, we must not take the fault..
70 	 */
71 	if (in_atomic() || !mm)
72 		goto bad_area_nosemaphore;
73 
74 	down_read(&mm->mmap_sem);
75 	vma = find_vma(mm, address);
76 	if (!vma)
77 		goto bad_area;
78 	if (vma->vm_start <= address)
79 		goto good_area;
80 	if (!(vma->vm_flags & VM_GROWSDOWN))
81 		goto bad_area;
82 	if (expand_stack(vma, address))
83 		goto bad_area;
84 /*
85  * Ok, we have a good vm_area for this memory access, so
86  * we can handle it..
87  */
88 good_area:
89 	info.si_code = SEGV_ACCERR;
90 
91 	if (write) {
92 		if (!(vma->vm_flags & VM_WRITE))
93 			goto bad_area;
94 	} else {
95 		if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
96 			goto bad_area;
97 	}
98 
99 survive:
100 	/*
101 	 * If for any reason at all we couldn't handle the fault,
102 	 * make sure we exit gracefully rather than endlessly redo
103 	 * the fault.
104 	 */
105 	switch (handle_mm_fault(mm, vma, address, write)) {
106 	case VM_FAULT_MINOR:
107 		tsk->min_flt++;
108 		break;
109 	case VM_FAULT_MAJOR:
110 		tsk->maj_flt++;
111 		break;
112 	case VM_FAULT_SIGBUS:
113 		goto do_sigbus;
114 	case VM_FAULT_OOM:
115 		goto out_of_memory;
116 	default:
117 		BUG();
118 	}
119 
120 	up_read(&mm->mmap_sem);
121 	return;
122 
123 /*
124  * Something tried to access memory that isn't in our memory map..
125  * Fix it, but check if it's kernel or user first..
126  */
127 bad_area:
128 	up_read(&mm->mmap_sem);
129 
130 bad_area_nosemaphore:
131 	/* User mode accesses just cause a SIGSEGV */
132 	if (user_mode(regs)) {
133 		tsk->thread.cp0_badvaddr = address;
134 		tsk->thread.error_code = write;
135 #if 0
136 		printk("do_page_fault() #2: sending SIGSEGV to %s for "
137 		       "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
138 		       tsk->comm,
139 		       write ? "write access to" : "read access from",
140 		       field, address,
141 		       field, (unsigned long) regs->cp0_epc,
142 		       field, (unsigned long) regs->regs[31]);
143 #endif
144 		info.si_signo = SIGSEGV;
145 		info.si_errno = 0;
146 		/* info.si_code has been set above */
147 		info.si_addr = (void __user *) address;
148 		force_sig_info(SIGSEGV, &info, tsk);
149 		return;
150 	}
151 
152 no_context:
153 	/* Are we prepared to handle this kernel fault?  */
154 	if (fixup_exception(regs)) {
155 		current->thread.cp0_baduaddr = address;
156 		return;
157 	}
158 
159 	/*
160 	 * Oops. The kernel tried to access some bad page. We'll have to
161 	 * terminate things with extreme prejudice.
162 	 */
163 	bust_spinlocks(1);
164 
165 	printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at "
166 	       "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n",
167 	       raw_smp_processor_id(), field, address, field, regs->cp0_epc,
168 	       field,  regs->regs[31]);
169 	die("Oops", regs);
170 
171 /*
172  * We ran out of memory, or some other thing happened to us that made
173  * us unable to handle the page fault gracefully.
174  */
175 out_of_memory:
176 	up_read(&mm->mmap_sem);
177 	if (is_init(tsk)) {
178 		yield();
179 		down_read(&mm->mmap_sem);
180 		goto survive;
181 	}
182 	printk("VM: killing process %s\n", tsk->comm);
183 	if (user_mode(regs))
184 		do_exit(SIGKILL);
185 	goto no_context;
186 
187 do_sigbus:
188 	up_read(&mm->mmap_sem);
189 
190 	/* Kernel mode? Handle exceptions or die */
191 	if (!user_mode(regs))
192 		goto no_context;
193 	else
194 	/*
195 	 * Send a sigbus, regardless of whether we were in kernel
196 	 * or user mode.
197 	 */
198 #if 0
199 		printk("do_page_fault() #3: sending SIGBUS to %s for "
200 		       "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n",
201 		       tsk->comm,
202 		       write ? "write access to" : "read access from",
203 		       field, address,
204 		       field, (unsigned long) regs->cp0_epc,
205 		       field, (unsigned long) regs->regs[31]);
206 #endif
207 	tsk->thread.cp0_badvaddr = address;
208 	info.si_signo = SIGBUS;
209 	info.si_errno = 0;
210 	info.si_code = BUS_ADRERR;
211 	info.si_addr = (void __user *) address;
212 	force_sig_info(SIGBUS, &info, tsk);
213 
214 	return;
215 vmalloc_fault:
216 	{
217 		/*
218 		 * Synchronize this task's top level page-table
219 		 * with the 'reference' page table.
220 		 *
221 		 * Do _not_ use "tsk" here. We might be inside
222 		 * an interrupt in the middle of a task switch..
223 		 */
224 		int offset = __pgd_offset(address);
225 		pgd_t *pgd, *pgd_k;
226 		pud_t *pud, *pud_k;
227 		pmd_t *pmd, *pmd_k;
228 		pte_t *pte_k;
229 
230 		pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset;
231 		pgd_k = init_mm.pgd + offset;
232 
233 		if (!pgd_present(*pgd_k))
234 			goto no_context;
235 		set_pgd(pgd, *pgd_k);
236 
237 		pud = pud_offset(pgd, address);
238 		pud_k = pud_offset(pgd_k, address);
239 		if (!pud_present(*pud_k))
240 			goto no_context;
241 
242 		pmd = pmd_offset(pud, address);
243 		pmd_k = pmd_offset(pud_k, address);
244 		if (!pmd_present(*pmd_k))
245 			goto no_context;
246 		set_pmd(pmd, *pmd_k);
247 
248 		pte_k = pte_offset_kernel(pmd_k, address);
249 		if (!pte_present(*pte_k))
250 			goto no_context;
251 		return;
252 	}
253 }
254